JP6282090B2 - Power supply device and image forming apparatus - Google Patents

Description

  The present invention relates to a power supply device and an image forming apparatus, and more particularly to a switching power supply device including a load switch at an output.

  The switching power supply is provided with a control circuit for controlling the output voltage to a constant voltage even when the output current changes. This control circuit is a comparison circuit that controls the reference voltage and the midpoint potential obtained by resistance-dividing the output voltage of the switching power supply to have the same potential.

  By the way, in a device equipped with a switching power supply, when the device ends its operation and a predetermined time elapses, it transitions to a power saving state. In the power saving state, control is known in which the output voltage of the switching power supply is changed to be lower than the rated voltage based on the voltage switching signal output from the control unit of the apparatus. As a control method, for example, there is a method of changing a voltage dividing ratio for resistance-dividing the output voltage of the switching power supply in the above-described comparison circuit, or a method of changing a reference voltage of the comparison circuit (for example, see Patent Document 1). There has also been proposed a method for reducing the loss of the switching power supply after the apparatus shifts to the power saving state. Thereby, efficient energy saving can be realized in the power saving state.

  When the device returns from the power saving state and starts to operate, an operation opposite to the above-described operation is performed based on the voltage switching signal output from the control unit of the device. That is, control is performed to return the output voltage of the switching power supply to the rated voltage from the dropped voltage.

JP 2002-199729 A

  FIG. 7 shows a method for changing and controlling the output voltage of the switching power supply based on the voltage switching signal output from the control unit of the apparatus. The detailed description of FIG. 7 will be described later. When the apparatus enters the power saving state, the control unit 1400 switches the voltage switching signal VCHG from the high level to the low level, and makes the output voltage VCC1 of the switching power supply 300 lower than the rated voltage. On the other hand, when the apparatus enters an operation state in which image formation is performed, control unit 1400 switches voltage switching signal VCHG from a low level to a high level, and returns output voltage VCC1 of switching power supply 300 to the rated voltage.

  Incidentally, the control unit 1400 of the device may not be able to grasp all the current consumed by the device. In this case, the control unit 1400 needs to control the voltage switching signal VCHG (hereinafter referred to as prediction control) by predicting the timing at which the circuit connected to the control unit 1400 stops. As shown in FIG. 8, when the device transitions from the operating state to the standby state, the current consumption of the control unit 1400 drops from the current I1 to the current I2. Further, immediately after the device transitions from the standby state to the power saving state, the current consumption of the control unit 1400 remains in the current I2 state when a part of the device is still driven. In this case, after the transition from the standby state to the power saving state, for example, after the elapse of time T1, all the loads are turned off and the current drops to the current I3. In such a case, the control unit 1400 changes the voltage switching signal VCHG from the high level to the low level after a time T2 longer than the time T1 with a margin, and changes the output voltage VCC1 from the rated voltage of 3.37V to 3 Lower to 22V. That is, as shown in FIG. 8, the transition to the state where the power drops most is after the time T <b> 2 elapses after the apparatus enters the power saving state.

  On the other hand, if the control unit 1400 drops the output voltage VCC1 of the switching power supply 300 for power saving even though the necessary operation of the circuit is not completed, the control unit 1400 may cause an electric wire or a circuit wiring route. In addition, a voltage drop occurs. As a result, the voltage of the control unit 1400 may drop too much and the circuit may not be able to operate. For this reason, as described above, after the transition to power saving, it is necessary to wait until all the control loads are turned off before dropping the output voltage VCC1 of the switching power supply 300. That is, after the consumption current drops to the current I3, the output voltage VCC1 needs to be dropped. In addition, there is a possibility that the output voltage of the switching power supply cannot be lowered when it is not possible to determine that all of the loads have been turned off in spite of the power saving state. In such a case, the power loss in the power saving state cannot be sufficiently reduced.

  The present invention has been made under such circumstances, and an object of the present invention is to efficiently reduce power consumption when the apparatus transitions to a power saving state.

  In order to solve the above-described problems, the present invention has the following configuration.

(1) A generator that generates a first DC voltage from an AC voltage, a feedback unit that controls the first DC voltage generated by the generator to be a target voltage, and the generator A switch that supplies or cuts off the generated first DC voltage to a load; and a control unit that controls connection or disconnection of the switch, and the feedback unit includes the first DC voltage via the switch. When the voltage is input and the first DC voltage is not input due to the switch being cut by the control means, the first DC voltage generated by the generating unit is reduced below a predetermined value. switching control in accordance with the Ruco is.
(2) An image forming apparatus including an image forming unit that forms an image on a recording medium, the generator generating a first DC voltage from an AC voltage, and the first DC voltage generated by the generator A feedback unit for controlling the first DC voltage generated by the generation unit to a load or a control unit for controlling connection or disconnection of the switch; The feedback unit receives the first DC voltage via the switch, and when the control unit cuts the switch, the first DC voltage is no longer input. The image forming apparatus characterized in that the first DC voltage generated by the generating unit is lowered below a predetermined value.

  ADVANTAGE OF THE INVENTION According to this invention, when an apparatus transfers to a power saving state, power consumption can be reduced efficiently.

Device configuration diagram using the power supply of the first embodiment Circuit diagram showing the power supply configuration of the first embodiment Sectional view of image forming apparatus of first embodiment, timing diagram of remote signal The flowchart which shows the remote signal processing of 1st embodiment Device configuration diagram using the power source of the second embodiment, circuit diagram showing the power source configuration Remote signal timing diagram of the second embodiment Device configuration diagram using conventional power source, circuit diagram showing power source configuration Timing diagram of conventional voltage switching signal

[Conventional switching power supply]
A configuration of a conventional switching power supply (hereinafter simply referred to as a power supply) will be described for comparison with embodiments described later. 7A is a device configuration diagram using a conventional power source, FIG. 7B is a circuit diagram showing the configuration of the conventional power source, and shows details of the power source 300 of FIG. 7A. It is.

  The AC voltage supplied from the commercial AC power supply via the AC plug 100 is reduced in noise by the filter circuit 200, converted into a DC voltage by the power supply 300, and the output voltage VCC1 is generated. The power supply 300 supplies the output voltage VCC1 to the control unit 1400, the control loads 500 and 510, the sensor 600, and the like. Here, the control loads 500 and 510 are loads controlled by the control unit 1400. The control unit 1400 outputs a voltage switching signal VCHG to the power supply 300, and performs voltage switching control of the output voltage VCC1. There are three states of the device on which the power supply 300 is mounted. The first is an operation state that is a first mode in which the apparatus executes image formation (including a preparation operation) and consumes predetermined power. The second is a standby state in which the apparatus is ready for operation and is waiting for the start of image formation. The third is a power saving state, which is a second mode in which the apparatus cuts off power supply to some loads. When the device transitions to the power saving state, the control unit 1400 switches the voltage switching signal VCHG from the high level to the low level, and makes the output voltage VCC1 of the power supply 300 lower than the rated voltage. Thereby, the output power of the power supply 300 is reduced, and the power of the apparatus is reduced. On the other hand, when the device transitions to the operating state, control unit 1400 switches voltage switching signal VCHG from the low level to the high level, and returns output voltage VCC1 of power supply 300 to the rated voltage.

The power supply 300 includes a comparison circuit 390. The comparison circuit 390 includes a transistor 359, resistors 357, 358, 360, a shunt regulator 355, a photocoupler 304, and the like. The comparison circuit 390 is a circuit for controlling the output voltage VCC1 of the power supply 300 to be a constant voltage. When the voltage switching signal VCHG output from the control unit 1400 is at a high level, the transistor 359 is turned on. When the transistor 359 is turned on, both ends of the resistor 358 are substantially short-circuited. In the comparison circuit 390, a voltage dividing circuit for the output voltage VCC1 of the power supply 300 including a resistor 360, a resistor 357, and a resistor 358 is formed. The comparison circuit 390 performs feedback control by comparing the potential of the voltage dividing circuit with the reference voltage Vref of the shunt regulator 355. The control unit 1400 controls the connection (when the transistor 359 is off) and the non-connection (when the transistor 359 is on) of the resistor 358 by outputting the voltage switching signal VCHG, and the output voltage VCC1 of the power supply 300 is controlled. Can be switched. When the voltage switching signal VCHG output from the control unit 1400 is at a low level (the transistor 359 is off), the output voltage VCC1 of the power supply 300 is
Vref × (resistor 360 + resistor 357 + resistor 358) / (resistor 357 + resistor 358)
It becomes the voltage.

On the other hand, when the voltage switching signal VCHG output by the control unit 1400 becomes high level, the transistor 359 is turned on, both ends of the resistor 358 are substantially short-circuited, and the output voltage VCC1 of the switching power supply 300 is
Vref × (resistance 360 + resistance 357) / resistance 357
It becomes the voltage.

  Here, consider a case where the resistor 360 is 10 kΩ, the resistor 357 is 5.9 kΩ, the resistor 358 is 430Ω, and Vref is 1.25V. In this case, when the voltage switching signal VCHG output from the control unit 1400 is at a high level, the output voltage VCC1 is controlled to 3.37V, which is a rated voltage. On the other hand, when the voltage switching signal VCHG signal output from the control unit 1400 is at a low level, the output voltage VCC1 is controlled to 3.22 V, which is lower in potential than the rated voltage.

  As described above, the control unit 1400 switches the voltage switching signal VCHG from the high level to the low level at the time of the power saving transition, thereby lowering the output voltage VCC1 from the rated voltage 3.37V to 3.22V. Further, when the apparatus returns from the power saving state to the operating state or the standby state, the control unit 1400 switches the voltage switching signal VCHG from the low level to the high level, thereby returning the output voltage of the switching power supply to the rated voltage of 3.37V. It can be performed.

[Conventional voltage switching signal output timing]
As described above, the control unit 1400 of the device may not be able to grasp all the current consumed by the device. In this case, the control unit 1400 needs to perform predictive control for controlling the voltage switching signal VCHG by predicting the timing at which the circuit connected to the control unit 1400 stops. This is because, when the power consumption is generated without turning off all the control loads of the apparatus in spite of the power saving state, or when the delay time until the control loads 500 and 510 are actually turned off occurs. Because there is.

  FIG. 8 shows the output timing of the voltage switching signal VCHG output by the control unit 1400 when the apparatus transitions to the power saving state. Specifically, FIG. 8A shows the state of the apparatus, FIG. 8B shows the voltage switching signal VCHG output by the control unit 1400, and FIG. 8C shows the output voltage VCC1 of the power supply 300. It is a figure which shows a voltage value. FIG. 8D is a diagram showing the current values of the current consumed by the control unit 1400, the control loads 500 and 510, and the sensor 600 to which the output voltage VCC1 is supplied, and FIG. 8E is the device consumed. It is a figure which shows electric power (power consumption). When the device state transitions from the operating state to the standby state, the consumption current drops from the current I1 to the current I2, as shown in FIG. Further, immediately after the device state transitions from the standby state to the power saving state, if a part of the load is still driven, the current consumption remains in the state of the current I2. In this case, after the transition from the standby state to the power saving state, after the time T1 has elapsed, all the loads are turned off, and the consumption current drops from the current I2 to the current I3. In such a case, the control unit 1400 changes the voltage switching signal VCHG from the high level to the low level after a time T2 longer than the time T1 has elapsed since the transition from the standby state to the power saving state. As a result, the control unit 1400 drops the output voltage VCC1 of the power supply 300 to 3.22V, which is lower than the rated voltage of 3.37V, as shown in FIG. 8C. Thereby, as shown in FIG.8 (e), the power consumption of an apparatus falls and the power saving property is improved. As shown in FIG. 8E, after the device transitions to the power saving state, the device transitions to a state where the power consumption of the device is the lowest after the time T2 by the predictive control as described above has elapsed.

[First embodiment]
[Device configuration]
FIG. 1 is a schematic diagram of an apparatus configuration using the power supply according to the first embodiment. In addition, the same code | symbol is attached | subjected to the same structure as the structure demonstrated in FIG. 7, and detailed description is abbreviate | omitted. The power supply 300 that is the generation unit of the present embodiment is a control unit that controls the first output voltage VCC1, which is a first DC voltage, and the second output voltage VCC2, which is a second DC voltage, as output voltages. Output to 400. When AC plug 100 is connected to an outlet, power supply 300 outputs first output voltage VCC1. A power switch 480 that is a main switch that can be operated by an operator is connected to the control unit 400. When the power switch 480 is pressed (also referred to as being turned on), the first output voltage VCC1 is supplied to the controller 400. The controller 400 operates to start the second output voltage VCC2 and supply the second output voltage VCC2 to the control loads 500 and 510 and the sensor 600, which are loads, as will be described later.

  When the power switch 480 is pressed from a state where the device is stopped (hereinafter also referred to as an off state), the transistor 402 is turned on, and the remote signal RMT1 which is the first signal is set to a low level. The transistor 402 has a collector terminal connected to the power supply 300, an emitter terminal grounded, and a base terminal connected to the power switch 480. When the power switch 480 is pressed to activate the device, the transistor 401 latches a remote signal RMT1 described later at a low level and maintains the supply of the second output voltage VCC2. The transistor 401 has a collector terminal connected to the collector terminal of the transistor 402 and the power supply 300, an emitter terminal grounded, and a base terminal connected to a LATCH terminal of a CPU 407 described later. In the transistor 405, when the power supply switch 480 is pressed in a state where the second output voltage VCC2 is supplied from the power supply 300 to the control unit 400 (hereinafter, this state is referred to as a start state of the second output voltage VCC2). Is detected. The transistor 405 has a collector terminal connected to the second output voltage VCC2 and a SWOFF terminal of a CPU 407 described later via a pull-up resistor 406, an emitter terminal grounded, and a base terminal connected to the power switch 480. When the control unit 400 detects that the power switch 480 has been pressed by the transistor 405 while the device is operating, the control unit 400 cancels the state in which the second output voltage VCC2 is continuously output and releases the second output voltage VCC2. The output of the output voltage VCC2 is stopped.

  The control unit 400 includes a CPU 407, and the CPU 407 is supplied with the second output voltage VCC2 output from the power supply 300. The CPU 407 has a SWOFF terminal connected to the collector terminal of the transistor 405 and a LATCH terminal connected to the base terminal of the transistor 401.

[Power supply configuration]
FIG. 2 is a detailed circuit diagram of the power supply 300 of the present embodiment. The AC voltage passing through the filter circuit 200 is rectified and smoothed by the bridge diode 301 and the smoothing capacitor 302 and applied to the primary winding 310 a of the transformer 310. The power supply control IC 303 controls a current flowing through the primary winding 310 a of the transformer 310 by controlling a switching operation for turning on or off a field effect transistor (hereinafter referred to as FET) 307 that is a switching element. The diode 309 and the capacitor 308 rectify and smooth the voltage induced in the auxiliary winding 310 c of the transformer 310 in order to operate the power supply control IC 303, and output it to the VCC terminal of the power supply control IC 303. A resistor 305 and a resistor 306 are driving resistors for the FET 307, and the gate terminal of the FET 307 is connected to the OUT terminal of the power supply control IC 303 via the resistor 305. The voltage induced in the secondary winding 310b of the transformer 310 is rectified and smoothed by a rectifier circuit including a diode 350 and a capacitor 351, and is output as the first output voltage VCC1.

  The power supply 300 is provided with a comparison circuit 398 that is a comparison unit for feeding back the output voltage and controlling the output voltage to be the target voltage. The comparison circuit 398 is a circuit that controls the reference voltage Vref and the midpoint potential obtained by resistance-dividing the first output voltage VCC1 of the power supply 300 to be the same potential. The comparison circuit 398 includes a shunt regulator 355, phase compensation constants (resistor 356, resistor 362, capacitor 354, capacitor 361), a photocoupler 304, and the like. The comparison circuit 398 compares the voltage divided by the plurality of resistors 360, 357, and 358 with the reference voltage Vref of the shunt regulator 355, and uses the differential voltage that is the comparison result as the photodiode of the photocoupler 304. Light 304a. When the photodiode 304a of the photocoupler 304 emits light, the phototransistor 304b of the primary side photocoupler 304 is turned on. When the phototransistor 304b is turned on, a signal is input to a feedback terminal (hereinafter referred to as an FB terminal) of the power supply control IC 303. In this way, by connecting the collector terminal of the phototransistor 304b of the photocoupler 304 to the FB terminal of the power supply control IC 303, the power supply control IC 303 performs feedback control and obtains the first output voltage VCC1 of a constant voltage from the secondary side. Can be output. The capacitor 354, the capacitor 361, the resistor 362, and the resistor 356 that constitute the constants for phase compensation described above are for stable operation of feedback control. Resistors 352 and 353 are resistors for driving the photocoupler 304.

  The load switch 366 configured by a P-channel FET that is the first FET is configured as a load switch that outputs the second output voltage VCC2. Here, the load switch is a semiconductor switch for turning on (supplying) or turning off (cutting off) the power to the load for the purpose of power saving, and for example, an FET which is a field effect transistor is used. When the control unit 400 sets the remote signal RMT1 to the low level, the load switch 366 is turned on, and the second output voltage VCC2 is supplied to the load. The constants of the resistor 363, the resistor 365, and the capacitor 364 form a time constant that soft-starts the load switch 366. The second output voltage VCC2 output when the load switch 366 is turned on is connected to a base terminal of a transistor 359 that is a first transistor that switches the resistance value of the voltage dividing resistor of the comparison circuit 398. Here, the collector terminal of the transistor 359 is connected to one end of the resistor 358, and the emitter terminal is grounded. Note that the second output voltage VCC2 is substantially equal to the first output voltage VCC1 when the voltage drop due to the on-resistance of the load switch 366 can be ignored.

(Device startup)
A mechanism in which the user activates the apparatus by pressing the power switch 480 will be described with reference to FIGS. The first output voltage VCC1 output from the power supply 300 is connected to the base terminal of the transistor 402 of the control unit 400 via the power switch 480. When the user presses the power switch 480, the first output voltage VCC1 charges the electrolytic capacitor 403 via the resistor 404. When charging of the electrolytic capacitor 403 is completed, the transistor 402 is turned on, and the remote signal RMT1 becomes low level. Note that since the electrolytic capacitor 403 is quickly charged, a time difference from when the power switch 480 is turned on to when the transistor 402 is turned on can be ignored. The remote signal RMT1 is connected to the gate terminal of the FET constituting the load switch 366, and the load switch 366 is turned on when the low level remote signal RMT1 is input. When the load switch 366 is turned on, the power supply 300 supplies the second output voltage VCC2 to the load (hereinafter, the second output voltage VCC2 is also activated).

  When the second output voltage VCC2 is activated, the second output voltage VCC2 is supplied to the CPU 407 of the control unit 400, and the CPU 407 is activated. Then, as will be described later, the CPU 407 performs control so that the second output voltage VCC2 is continuously output. The output second output voltage VCC2 is supplied to the control loads 500 and 510 and the sensor 600. Then, the CPU 407 controls the control load 500 and the control load 510 based on the state of the sensor 600. When the apparatus in which the power supply 300 of this embodiment is mounted is an image forming apparatus, for example, the sensor 600 includes, for example, a sensor that detects the presence or absence of paper, a sensor that detects temperature and humidity, and a housing for the image forming apparatus. This corresponds to a sensor that detects opening and closing of the body door. The control load 500 and the control load 510 correspond to, for example, a roller for transporting paper, a motor for driving a photosensitive member, a motor for rotating a polygon mirror, and a laser.

(Configuration of image forming apparatus)
Here, a configuration of an image forming apparatus as an apparatus in which the power supply 300 is mounted will be described. FIG. 3A is a cross-sectional view illustrating a schematic configuration of the image forming apparatus. When the image forming apparatus 1 receives an image signal from the image forming unit, the sheet 8 as a recording medium is separated and fed one by one from the sheet feeding unit 2 by the sheet feeding roller 7, and a conveying unit including a conveying roller, a registration roller, and the like. Thus, the sheet 8 is conveyed. The optical unit 6 in the image forming apparatus 1 irradiates the photosensitive drum 4 in the process cartridge 3 with laser light based on the image signal. Thereby, an electrostatic latent image is formed on the photosensitive drum 4. The electrostatic latent image is developed on the photosensitive drum 4 by a developer, that is, toner, contained in the process cartridge 3 to form a toner image. The toner image formed on the photosensitive drum 4 is transferred to the sheet 8 by the transfer roller 9, and the sheet 8 on which the toner image is transferred is conveyed to the fixing device 5. The fixing device 5 includes a ceramic heater (not shown) as a heat source, a heat-resistant film material that includes the ceramic heater, and a pressure roller disposed to face the ceramic heater. The toner image transferred to the sheet 8 is heated and pressurized by the fixing device 5 and fixed on the sheet 8. The sheet 8 for which the fixing process has been completed is discharged to a discharge tray via the conveyance roller of the image forming apparatus 1.

  1 and 2 drives a conveyance roller of the image forming apparatus 1, a motor (not shown) for driving the paper feed roller 7, a conveyance sensor (not shown) used for conveyance control of the sheet 8, and the like. It is a power source for. The power switch 480 is a push switch that is turned on (contact is closed) only while the user is pressing the switch, and is turned off (contact is opened) when the user releases the switch. However, the transistor 402 maintains the on state of the transistor 402 until the discharge of the electrolytic capacitor 403 is completed. When the transistor 402 is turned on and the remote signal RMT1 becomes low level and the second output voltage VCC2 is activated as described above, the CPU 407 is activated. Then, the CPU 407 outputs a high-level LATCH signal from the LATCH terminal 452 connected to the base terminal of the transistor 401, and turns on the transistor 401. When the transistor 401 is turned on, the remote signal RMT1 is maintained (latched) at a low level, and the second output voltage VCC2 is kept activated (a state in which the second output voltage VCC2 is supplied to the load). Is done. Here, the time until the CPU 407 turns on the transistor 401 needs to be shorter than the discharge time of the electrolytic capacitor 403.

(Device stop)
In the state where the second output voltage VCC2 is activated by the control unit 400 and the second output voltage VCC2 output from the power supply 300 is supplied to the load, the user presses the power switch 480 to stop the apparatus. explain. When the user presses the power switch 480 while the first output voltage VCC1 and the second output voltage VCC2 are being output from the power supply 300, the controller 400 operates as follows. A connection point between the pull-up resistor 406 and the collector terminal of the transistor 405 is connected to the SWOFF terminal of the CPU 407. Therefore, when the user presses the power switch 480, the transistor 405 is turned on, and the voltage of the SWOFF terminal of the CPU 407 changes from high level to low level. As a result, the CPU 407 detects that the user has pressed the power switch 480. When the CPU 407 detects that the power switch 480 is pressed, the second output voltage VCC2 is continuously output, that is, the LATCH signal latching the remote signal RMT1 at the low level is changed from the high level to the low level. Switch to. When the CPU 407 sets the LATCH signal to a low level, the transistor 401 is turned off. The transistor 401 is an open collector. When the transistor 401 is turned off, the collector terminal of the transistor 401 becomes high impedance, but the remote signal RMT1 becomes high level by the resistor 363. When the remote signal RMT1 becomes high level, the load switch 366 is turned off. That is, when the power switch 480 is pressed while the second output voltage VCC2 is being output, the output of the second output voltage VCC2 is stopped.

[Comparison with conventional example]
As described with reference to FIG. 7B, in the conventional example, the output voltage of the power supply 300 is controlled based on the voltage switching signal VCHG from the control unit 400, and the output voltage VCC1 is controlled to increase or decrease. On the other hand, in the present embodiment, the second output voltage VCC2 output when the load switch 366 is turned on is connected to the base terminal of the transistor 359. That is, in the present embodiment, control is performed to increase or decrease the first output voltage VCC1 of the power supply 300 based on the second output voltage VCC2, in other words, according to the state of the load switch 366. The second output voltage VCC2 is input to the base terminal of the transistor 359 to turn on or off the transistor 359, and corresponds to the voltage switching signal of the conventional example. That is, the comparison circuit 398 includes a control circuit that detects that the load switch 366 is turned off and the output of the second output voltage VCC2 is cut off, and lowers the first output voltage VCC1 below the rated output voltage. Yes. As described above, the comparison circuit 398 also functions as a voltage changing unit that reduces the first output voltage VCC1 from a predetermined value when the load switch 366 is disconnected. The mechanism for realizing such control is that the output voltage of the first output voltage VCC1 is raised or lowered by turning on or off the transistor 359 according to the second output voltage VCC2.

When the load switch 366 is turned off and the second output voltage VCC2 is not supplied (also referred to as off), the transistor 359 is turned off. For this reason, the output voltage of the first output voltage VCC1 is
Vref × (resistor 360 + resistor 357 + resistor 358) / (resistor 357 + resistor 358)
It becomes the voltage. On the other hand, when the load switch 366 is turned on and the second output voltage VCC2 is supplied (also referred to as on), the transistor 359 is turned on. Therefore, the first output voltage VCC1 is
Vref × (resistance 360 + resistance 357) / resistance 357
It becomes. These states are collectively shown in the mode table of Table 1.

表１は、左列から順に、ロードスイッチ３６６の状態（オン（ＯＮ）又はオフ（ＯＦＦ））、第二の出力電圧ＶＣＣ２の状態（供給されている（ＯＮ）又は供給されていない（ＯＦＦ））を示している。更に、表１は、トランジスタ３５９の状態（オン（ＯＮ）又はオフ（ＯＦＦ））、第一の出力電圧ＶＣＣ１の状態（計算式及び具体的数値）を示している。なお、表１の具体的な数値は、Ｖｒｅｆの電圧値を１．２５Ｖ、抵抗３６０の抵抗値を１０ｋΩ、抵抗３５７の抵抗値を５．９ｋΩ、抵抗３５８の抵抗値を４３０Ω、として計算式に代入し算出している。このように、ロードスイッチ３６６の状態に応じて、第一の出力電圧ＶＣＣ１を分圧する抵抗の分圧比が変更される。

Table 1 shows, in order from the left column, the state of the load switch 366 (ON (ON) or OFF (OFF)), the state of the second output voltage VCC2 (supplied (ON) or not supplied (OFF)) ). Further, Table 1 shows the state of the transistor 359 (ON (ON) or OFF (OFF)) and the state of the first output voltage VCC1 (calculation formula and specific numerical values). The specific numerical values in Table 1 are calculated by assuming that the voltage value of Vref is 1.25 V, the resistance value of the resistor 360 is 10 kΩ, the resistance value of the resistor 357 is 5.9 kΩ, and the resistance value of the resistor 358 is 430Ω. Substitute and calculate. Thus, the voltage dividing ratio of the resistor that divides the first output voltage VCC1 is changed according to the state of the load switch 366.

  When it is time to end the operation of the apparatus and shift to the power saving state, the control unit 400 of the apparatus sets the remote signal RMT1 to the high level in order to decrease the voltage of the power supply 300. When the control unit 400 sets the remote signal RMT1 to the high level, the load switch 366 is turned off. As a result, the power supply 300 outputs only the first output voltage VCC1, and the second output voltage VCC2 is not output. Thereby, the transistor 359 is turned off, the first output voltage VCC1 drops (for example, 3.22 V (Table 1)), and a low-loss power saving state is set.

  On the other hand, when the device returns from the power saving state to the operating state or the standby state, the remote signal RMT1 from the control unit 400 of the device becomes low level, the load switch 366 is turned on, and the second output voltage VCC2 is Supplied. As a result, the transistor 359 is turned on, and the first output voltage VCC1 returns to the operation state in which the output voltage has increased from the state in which the output voltage has decreased (for example, 3.37 V (Table 1)).

  In the present embodiment, a load switch 366 is provided, and the supply of the second output voltage VCC2 to all loads connected to the second output voltage VCC2 can be cut off. Then, the first output voltage VCC1 of the power supply 300 can be lowered with the load switch 366 being turned off, that is, the supply of the second output voltage VCC2 to all loads being turned off. That is, in the present embodiment, the control unit 400 does not need to perform prediction that the load current consumption is turned off, and the time T2 for predictive control as described with reference to FIG. It is possible to transition to. In the configuration of the present embodiment, the first output voltage VCC1 can be lowered after the second output voltage VCC2 serving as the power source for the control loads 500 and 510 is reliably turned off.

[Transition to power saving state]
FIG. 3B is a timing chart of this embodiment. Specifically, FIGS. 3B and 3A are diagrams illustrating the state of the apparatus, FIGS. 3B and 3B are diagrams illustrating the waveform of the remote signal RMT1 output from the control unit 400, and FIGS. c) is a diagram showing a voltage value of the first output voltage VCC1 of the power supply 300. FIG. 3B and 3D are diagrams showing the current values of the current consumed by the control unit 400, the control loads 500 and 510, and the sensor 600, and FIGS. 3B and 3E show the power consumed by the apparatus. FIG. The difference from the conventional example in FIG. 8 is as follows. In the conventional example shown in FIG. 8, the time T1 when the load of the control unit 1400 is turned off is predicted, and after the time T2 for predictive control longer than the time T1, the voltage switching signal VCHG is changed from the high level to the low level. I was switching. On the other hand, in FIG. 3B of the present embodiment, the first output voltage VCC1 is lowered immediately after the control unit 400 makes a transition from the low level to the high level without predicting the timing. The point that can be different. That is, in the present embodiment, when the second output voltage VCC2 is turned off, all the loads to which the second output voltage VCC2 is supplied are turned off and the operation is stopped, and the current consumption changes from the current I2 to the current I3. (FIGS. 3B and 3D). As a result, the first output voltage VCC1 can be lowered immediately after transition from the standby state to the power saving state (FIGS. 3B and 3C), and the power consumption of the device is also changed from the standby state to the power saving state. It can be reduced immediately after the transition (FIGS. 3B and 3E).

[Remote processing to reduce power consumption]
FIG. 4 shows a flowchart of remote processing which is control processing of the remote signal RMT1 executed by the control unit 400. In step (hereinafter referred to as S) 402, control unit 400 determines whether or not the apparatus satisfies a condition for shifting to the power saving state. Here, the condition for the apparatus to shift to the power saving state is as follows when the apparatus is the image forming apparatus 1. For example, when the image forming apparatus 1 finishes the printing operation and the control unit 400 refers to a timer (not shown) or the like, a transition to a power saving state is made when a predetermined time has passed without an instruction to start image formation. The conditions are as follows. A condition for shifting to the power saving state is that a predetermined time has passed without an instruction to start image formation after returning from the power saving state to the standby state.

  If the control unit 400 determines in S402 that the above-described condition is satisfied, the control unit 400 changes the remote signal RMT1 from the low level to the high level in S403. Note that changing the remote signal RMT1 from a low level to a high level is also referred to as turning off the remote signal RMT1 in this embodiment. When the control unit 400 turns off the remote signal RMT1 in S403, the load switch 366 is turned off, and the supply of the second output voltage VCC2 from the power supply 300 is stopped. When the supply of the second output voltage VCC2 is stopped, that is, when the input to the base terminal of the transistor 359 becomes a low level, the transistor 359 is turned off and the first output voltage VCC1 drops (Table 1). In the present embodiment, the determination time for the control unit 400 to decrease the first output voltage VCC1 of the power supply 300 (predictive control time T2 in FIG. 8B) is unnecessary, and after the transition to the power saving state. Power consumption is reduced in a time shorter than the time T2 (FIGS. 3B and 3E).

  On the other hand, when determining in S402 that the condition for shifting to the power saving state is not satisfied, the control unit 400 determines whether or not the condition for returning from the power saving state is satisfied in S410. Here, the condition for returning from the power saving state is, for example, a condition that the image forming apparatus 1 has received a print job or that a user has operated a key on the operation unit. When the control unit 400 determines in S410 that the condition for returning from the power saving state is not satisfied, the process returns to the process of S402. When the control unit 400 determines in S410 that the condition for returning from the power saving state is satisfied, the control unit 400 changes the remote signal RMT1 from the high level to the low level in S411. Note that changing the remote signal RMT1 from high level to low level is also referred to as turning on the remote signal RMT1 in this embodiment. When the control unit 400 turns on the remote signal RMT1 in S411, the load switch 366 is turned on, and supply of the second output voltage VCC2 from the power supply 300 is started. When the supply of the second output voltage VCC2 is started, that is, when the input to the base terminal of the transistor 359 becomes high level, the transistor 359 is turned on, and the first output voltage VCC1 rises, that is, returns to the rated voltage ( Table 1).

  As described above, according to the present embodiment, it is possible to efficiently reduce power consumption when the apparatus transitions to a power saving state.

[Second Embodiment]
In the first embodiment, the method of reducing the power by reducing the output voltage of the power supply 300 when the apparatus shifts to the power saving state has been described. In general, when the image forming apparatus continuously performs image forming operations, the output current of the power supply 300 is the maximum of the set current range, and the first output in the current path from the power supply 300 to the control unit 400 is performed. The voltage drop of the voltage VCC1 is also maximized. This voltage drop is due to the impedance of the wire, the contact resistance of the connector, the wiring resistance of the printed circuit board, the on-resistance of the FET used for the load switch, and the like. When the current consumption of the control unit 400 increases, this voltage drop cannot be ignored. In such a case, the first output voltage VCC1 of the power source 300 may be designed to be increased by, for example, 0.1 V or 0.2 V in advance so as to cancel the voltage drop caused by the above-described factors. .

  When the control unit 400 is operating at the set maximum current, a potential difference (hereinafter also referred to as an offset potential difference) corresponding to a voltage drop that has been increased in advance can be canceled. However, for example, when the device transitions to the standby state, the current consumption of the control unit 400 decreases, and for example, an offset voltage of 0.1 V or 0.2 V cannot be canceled, resulting in a high first output voltage VCC1. There is a case. In the present embodiment, a configuration taking these into account will be described.

  In the first embodiment, when the load switch 366 is off, the first output voltage VCC1 of the power supply 300 is lowered, and when the load switch 366 is on, the first output voltage VCC1 of the power supply 300 is set to the rated voltage. The example to return was explained. This embodiment assumes a device in which the current consumption of the control unit 400 is particularly large and there are a plurality of load switches. In the power saving state in which all the load switches are turned off, the output voltage of the power supply 300 is lowered as in the first embodiment. On the other hand, in an operation state in which all the load switches are turned on, the first output voltage VCC1 of the power supply 300 is increased in order to reduce the influence of the voltage drop described above. Further, in a standby state where only some of the load switches operate, the output voltage of the power supply 300 is returned to the rated voltage. In the present embodiment, the standby state in which the output voltage of the power source 300 has returned to the rated voltage is the first mode, the power saving state is the second mode, and the maximum value in which the output current of the power source 300 is set. The operating state is equivalent to the third mode.

  Also in this embodiment, the output voltage of the power supply 300 is controlled by the state of the load switch without using the voltage switching signal VCHG output from the control unit 1400 as in the conventional example. Further, in this embodiment, since the number of load switches is increased as compared with the first embodiment, a method using a logic gate is proposed. In this method, the output voltage of the power supply 300 is increased when the device is in the operating state, and the rated voltage is restored when the device transitions from the operating state to the standby state. As described above, since an unnecessary increase in the output voltage can be suppressed even in the standby state, the power consumption of the apparatus can be further reduced.

[Device configuration]
FIG. 5A is a schematic diagram of an apparatus configuration using the power supply of the present embodiment. In addition, the same code | symbol is attached | subjected to the same structure as the structure demonstrated in FIG. 1, and description is abbreviate | omitted. In FIG. 5A, the configuration different from the first embodiment is the following three points. The first point is that the third output voltage VCC3 is output from the power supply 300. The second point is that a remote signal RMT2 as a second signal is output from the control unit 400 to the power supply 300. The CPU 407 has an RMT2 terminal connected to the base terminal of the transistor 410, and when the power supply 300 is operating at the set maximum current due to continuous operation of the device, the CPU 407 has a high level from the RMT2 terminal. A signal is output and the transistor 410 is turned on. When the transistor 410 is turned on, the remote signal RMT2 becomes low level. On the other hand, when the apparatus is in a standby state or a power saving state, the CPU 407 outputs a low level signal from the RMT2 terminal, and turns off the transistor 410. The transistor 410 is an open collector, and when the transistor 410 is turned off, the collector terminal of the transistor 410 becomes high impedance, but the remote signal RMT2 becomes high level by the resistor 384 described later.

  The third point is that the third output voltage VCC3 is supplied to the control loads 500 and 510. Others are the same as in the first embodiment. The second output voltage VCC2 is controlled by a remote signal RMT1 from the control unit 400, and the third output voltage VCC3 is controlled by a remote signal RMT2 from the control unit 400. Note that the third output voltage VCC3 is substantially equal to the first output voltage VCC1 when a voltage drop due to an on-resistance of a load switch 387, which will be described later, can be ignored.

[Power supply configuration]
In FIG. 5B, as compared with the circuit diagram described in FIG. 2 of the first embodiment, the comparison circuit 395 includes a logic gate composed of an AND gate 382 that is a logical product circuit and an OR gate 383 that is a logical sum circuit. A gate has been added. In addition, a load switch 387 configured by a P-channel FET that is a second FET is added. Here, the resistor 384, the resistor 386, and the capacitor 385 are time constant circuits for soft start of the load switch 387. Further, the transistor 381 which is the second transistor of the comparison circuit 395 is a transistor activated by the AND gate 382. The transistor 381 controls connection of the resistor 380 (when the transistor 381 is off) and non-connection (when the transistor 381 is on). The transistor 359 of the comparison circuit 395 is a transistor driven by the OR gate 383, and controls the connection state (when the transistor 359 is off) and non-connection (when the transistor 359 is on) of the resistor 358. The first output voltage VCC1 of the power supply 300 is determined by the four resistors of the resistor 360, the resistor 357, the resistor 358, and the resistor 380, and the resistor 380 is increased from that of the first embodiment.

  More specifically, in the present embodiment, the resistor that divides the first output voltage VCC1 includes a plurality of resistors 380, 360, 357, and 358. The AND gate 382 receives the second output voltage VCC2 and the third output voltage VCC3, and the OR gate 383 receives the second output voltage and the third output voltage. The transistor 359 has a collector terminal connected to one end of the resistor 358, an emitter terminal grounded, and a base terminal connected to the output terminal of the OR gate 383. The transistor 381 has an emitter terminal connected to the first output voltage, a collector terminal connected to one end of the resistor 380, and a base terminal connected to the output terminal of the AND gate 382.

  The AND gate 382 and the OR gate 383 switch the resistor 380 and the resistor 358 to one of the connection / disconnection states according to the two output states of the load switch 366 and the load switch 387, and the first output voltage VCC1 of the power supply 300 Is changing. With this configuration, the first output voltage VCC1 can be controlled as follows. When both the load switch 366 and the load switch 387 are turned on, that is, when the power supply 300 is operating at the maximum current, the AND gate 382 outputs a high level, and the transistor 381 is turned off. The resistor 380 is connected. On the other hand, the OR gate 383 outputs a high level, turns on the transistor 359, and disconnects the resistor 358. Thereby, the comparison circuit 395 increases the first output voltage VCC1. When both the load switch 366 and the load switch 387 are off, that is, when the device is in the power saving state, the AND gate 382 outputs a low level, turns on the transistor 381, and disconnects the resistor 380. On the other hand, the OR gate 383 outputs a low level, the transistor 359 is turned off, and the resistor 358 is connected. Thereby, the comparison circuit 395 lowers the first output voltage VCC1.

  Further, when only one of the load switch 366 and the load switch 387 is on, that is, when the device is in a standby state, the AND gate 382 outputs a low level, turns on the transistor 381, and disconnects the resistor 380. And On the other hand, the OR gate 383 outputs a high level, turns on the transistor 359, and disconnects the resistor 358. Thus, the comparison circuit 395 can be configured to return the first output voltage VCC1 to the rated voltage. Table 2 shows a detailed mode table.

表２は、表１に比べて、ロードスイッチ３８７の状態（オン（ＯＮ）又はオフ（ＯＦＦ））、第三の出力電圧ＶＣＣ３の状態（供給されている（ＯＮ）又は供給されていない（ＯＦＦ））が追加されている。更に、表２は、表１に比べて、トランジスタ３８１の状態（オン（ＯＮ）又はオフ（ＯＦＦ））が追加されている。また、第一の出力電圧ＶＣＣ１の計算例として、抵抗３８０の抵抗値を４３０Ωとしており、その他の値は表１と同様である。

Compared to Table 1, Table 2 shows the state of the load switch 387 (ON (ON) or OFF (OFF)) and the state of the third output voltage VCC3 (supplied (ON) or not supplied (OFF). )) Has been added. Further, in Table 2, the state of the transistor 381 (ON (ON) or OFF (OFF)) is added as compared with Table 1. As a calculation example of the first output voltage VCC1, the resistance value of the resistor 380 is 430Ω, and other values are the same as those in Table 1.

[Transition to power saving state]
FIG. 6 is a timing chart of the present embodiment. In detail, FIG. 6A and FIG. 6C to FIG. 6E are the same as FIG. 3B of the first embodiment, and the description is omitted. FIG. 6B-1 is a diagram illustrating the remote signal RMT1 output from the control unit 400. FIG. 6B-2 is a diagram illustrating the remote signal RMT2 output by the control unit 400.

  The difference from FIG. 3B is that the first output voltage VCC1 is raised when the device operates at the set maximum current, that is, when the device is in an operating state (for example, 3. 46V). The first output voltage VCC1 is lowered when the device shifts from the operating state to the power saving state, and the output voltage is returned to the rated voltage when the device shifts to the standby state. This is the same as in the first embodiment. As described above, this embodiment is different from the first embodiment in that the first output voltage VCC1 is changed to a three-stage output voltage according to the operating state of the apparatus. By making the control voltage in three fine steps, more effective control of the power supply 300 is possible. In the present embodiment, the first output voltage VCC1 is increased or decreased depending on the state of the apparatus, that is, the size of the load. Thereby, not only the power saving control of the power supply 300 but also the condition that the voltage has been raised in advance by the voltage drop of the power supply 300 can be made only at the maximum load. That is, in this embodiment, the voltage control is increased and decreased, and is optimized according to the load. In the present embodiment, when shifting to the power saving state, the first output voltage VCC1 of the power supply 300 becomes the lowest voltage (eg, 3.22V). Further, when the load on the apparatus is in the maximum operating state within the setting, the first output voltage VCC1 of the power supply 300 is the highest voltage (eg, 3.46V).

  Also in the present embodiment, when shifting to the power saving state, the load switches 366 and 387 are turned off and all loads are disconnected, so that the control unit 400 determines whether or not the loads are operating. There is no need. For this reason, the first output voltage VCC1 can be immediately lowered without waiting for the prediction control time T2 to elapse when the state is shifted to the power saving state.

  Here, there may be a case where the control unit 400 cannot grasp the time during which a part of the load is operating immediately before the device shifts to the power saving state, and the load switch cannot be immediately turned off. In such a case, a load whose operation cannot be grasped is connected to, for example, the second output voltage VCC2 that is output when the load switch 366 is on. The third output voltage VCC3 output when the load switch 387 is on is connected with a load that can be immediately turned off when the power switch is entered. By connecting in this way, the following control can be performed. That is, when shifting to the power saving state, after turning off the load switch 387, the control unit 400 turns off the load switch 366 after turning off the load switch 366 based on predictive control as in the conventional example. It is also possible to use a two-stage control of “Yes”. In the present embodiment, the first output voltage VCC1 is sequentially lowered in two stages of 3.46V → 3.37V → 3.22V by a combination of logic circuits (AND gate 382 and OR gate 383). be able to. On the other hand, in the conventional example, the control unit 1400 delays the drop of the output voltage VCC1 by predictive control, and can only perform control in one stage, for example, 3.46V⇒3.22V. In this embodiment, the power consumption can be reduced by sequentially decreasing the output voltage at each stage, and the power saving can be further improved.

  As described above, according to the present embodiment, it is possible to efficiently reduce power consumption when the apparatus transitions to a power saving state.

300 switching power supply 366 load switch 398 comparison circuit 400 control unit

Claims (25)

A generator for generating a first DC voltage from the AC voltage;
A feedback unit for controlling the first DC voltage generated by the generating unit to be a target voltage;
A switch for supplying or cutting off the first DC voltage generated by the generating unit;
Control means for controlling connection or disconnection of the switch;
With
The feedback unit receives the first DC voltage via the switch, and when the control unit cuts the switch, the first DC voltage is no longer input. power supply, wherein the benzalkonium lower than a predetermined value the first DC voltage generated. The feedback unit reduces the first DC voltage generated by the generation unit below the predetermined value in response to a decrease in voltage supplied to the load due to disconnection of the switch. The power supply device according to claim 1. The feedback unit includes:
A resistor that divides the voltage generated by the generator;
3. The power supply device according to claim 1, wherein when the switch is disconnected by the control unit, the voltage dividing ratio of the resistor is changed. The switch has a FET,
The FET is turned on or off in accordance with a signal input from the control means to the gate terminal of the FET ,
The generator includes a power supply device according to claim 3, wherein the FET is in the on, and supplying the first DC voltage to the load through the FET. The resistor comprises a plurality of resistors,
The feedback unit includes:
Yes first end of the resistor of the plurality of resistors in the collector terminal is connected, an emitter terminal grounded, the first transistor, wherein said first DC voltage is supplied through the FET to the base terminal And
A state in which the first transistor is the first resistance when on is another resistor and disconnection of the plurality of resistors, said first transistor is the first resistor in the off wherein in the plurality of states that are connected to other resistors of the resistor, the power supply device according to claim 4, the voltage dividing ratio of the resistance, wherein Rukoto changed. It said switch having a first FET and a second FET,
The first FET is turned on or off according to a first signal input from the control means to the gate terminal of the first FET ,
The generation unit supplies the first DC voltage to the first load through the first FET when the first FET is on,
The second FET is turned on or off according to a second signal input from the control means to the gate terminal of the second FET ,
4. The power supply according to claim 3, wherein the generation unit supplies the first DC voltage to the second load via the second FET when the second FET is on. 5. apparatus. The resistor comprises a plurality of resistors,
The feedback unit includes:
A logical product circuit, wherein said first DC voltage said first DC voltage and via the second FET through the first FET is input,
A logical sum circuit said first DC voltage first the first DC voltage through the FET and via said second FET is input,
A first transistor having a collector terminal connected to one end of a first resistor of the plurality of resistors, an emitter terminal grounded, and a base terminal connected to an output terminal of the OR circuit;
The first DC voltage is supplied to an emitter terminal, one end of a second resistor different from the first resistor among the plurality of resistors is connected to a collector terminal, and an output of the AND circuit is connected to a base terminal A second transistor having a terminal connected thereto;
Have
A state in which the first transistor is the first resistance when on the other resistor and disconnected except for the first resistor of said plurality of resistors, said first transistor is off A state in which the first resistor is connected to a resistor other than the first resistor of the plurality of resistors, and the second resistor is connected to the plurality of resistors when the second transistor is on. a state in which the other resistor and disconnected excluding the second resistor of resistance, the second resistance of the second transistor is the second resistance in the off among the plurality of resistors a on purpose other resistance-like connected except, the partial pressure ratio of each of the resistance change power supply device according to claim 6, wherein Rukoto.   The generation unit includes a transformer having a primary winding and a secondary winding, a switching element that performs a switching operation for turning on or off a current flowing through the primary winding, and a control unit that controls the switching operation. The power supply device according to claim 1, wherein the power supply device is a switching power supply. An image forming apparatus comprising image forming means for forming an image on a recording medium,
A generator for generating a first DC voltage from the AC voltage;
A feedback unit for controlling the first DC voltage generated by the generating unit to be a target voltage;
A switch for supplying or cutting off the first DC voltage generated by the generating unit;
Control means for controlling connection or disconnection of the switch;
With
The feedback unit receives the first DC voltage via the switch, and when the control unit cuts the switch, the first DC voltage is no longer input. an image forming apparatus comprising a benzalkonium lower than a predetermined value the first DC voltage generated. The feedback unit reduces the first DC voltage generated by the generation unit below the predetermined value in response to a decrease in voltage supplied to the load due to disconnection of the switch. The image forming apparatus according to claim 9. The feedback unit includes:
A resistor that divides the voltage generated by the generator;
11. The image forming apparatus according to claim 9, wherein the voltage dividing ratio of the resistor is changed when the switch is disconnected by the control unit.   The control means connects the switch in a first mode that consumes predetermined power, and shuts off the switch in a second mode that reduces power consumption than the first mode. 12. The image forming apparatus according to any one of 11 above. The switch has a FET,
The FET is turned on or off in accordance with a signal input from the control means to the gate terminal of the FET ,
The generating unit, when the FET is on, an image forming apparatus according to claim 11, wherein the supplying the first DC voltage to the load through the FET. A main switch for connecting or cutting off the supply of the first DC voltage to the control means;
The image forming apparatus according to claim 13, wherein the control unit outputs the signal to turn on the FET when the first DC voltage is supplied from the main switch. The control means includes a transistor in which the main switch is connected to a base terminal, the signal is input to a collector terminal, and an emitter terminal is grounded.
15. The transistor is turned on by supplying the first DC voltage to the base terminal of the transistor by the main switch, and the signal is turned to a low level to turn on the FET. The image forming apparatus described in 1. The control means has a capacitor connected to the base terminal of the transistor,
The image forming apparatus according to claim 15, wherein the signal is latched at a low level before the discharge of the capacitor is finished. The resistor comprises a plurality of resistors,
The feedback unit includes:
Yes first end of the resistor of the plurality of resistors in the collector terminal is connected, an emitter terminal grounded, the first transistor, wherein said first DC voltage is supplied through the FET to the base terminal And
A state in which the first transistor is the first resistance when on is another resistor and disconnection of the plurality of resistors, said first transistor is the first resistor in the off wherein in the plurality of states that are connected to other resistors of the resistor, the image forming apparatus according to any one of claims 13 to 16 dividing ratio of the resistance, wherein Rukoto changed. It said switch having a first FET and a second FET,
The first FET is turned on or off according to a first signal input from the control means to the gate terminal of the first FET ,
The generation unit supplies the first DC voltage to the first load through the first FET when the first FET is on,
The second FET is turned on or off according to a second signal input from the control means to the gate terminal of the second FET ,
The image according to claim 11, wherein the generation unit supplies the first DC voltage to the second load via the second FET when the second FET is on. Forming equipment. A main switch for connecting or cutting off the supply of the first DC voltage to the control means;
The said control means outputs said 1st signal in order to turn ON said 1st FET, when said 1st DC voltage is supplied by the said main switch, The said 1st signal is output. Image forming apparatus. The control means includes a transistor in which the main switch is connected to a base terminal, the first signal is input to a collector terminal, and an emitter terminal is grounded.
The transistor is turned on when the first DC voltage is supplied to the base terminal of the transistor by the main switch, and the first FET is turned on when the first signal becomes low level. The image forming apparatus according to claim 19. The control means has a capacitor connected to the base terminal of the transistor,
21. The image forming apparatus according to claim 20, wherein the first signal is latched at a low level before the discharge of the capacitor is finished.   The said control means outputs said 2nd signal in order to turn on or off said 2nd FET according to the output current of the said production | generation part, The any one of Claims 19 thru | or 21 characterized by the above-mentioned. The image forming apparatus described in 1. The resistor comprises a plurality of resistors,
The feedback unit includes:
A logical product circuit, wherein said first DC voltage said first DC voltage and via the second FET through the first FET is input,
A logical sum circuit said first DC voltage first the first DC voltage through the FET and via said second FET is input,
A first transistor having a collector terminal connected to one end of a first resistor of the plurality of resistors, an emitter terminal grounded, and a base terminal connected to an output terminal of the OR circuit;
The first DC voltage is supplied to an emitter terminal, one end of a second resistor different from the first resistor among the plurality of resistors is connected to a collector terminal, and an output of the AND circuit is connected to a base terminal A second transistor having a terminal connected thereto;
Have
A state in which the first transistor is the first resistance when on the other resistor and disconnected except for the first resistor of said plurality of resistors, said first transistor is off A state in which the first resistor is connected to a resistor other than the first resistor of the plurality of resistors, and the second resistor is connected to the plurality of resistors when the second transistor is on. a state in which the other resistor and disconnected excluding the second resistor of resistance, the second resistance of the second transistor is the second resistance in the off among the plurality of resistors a on purpose other resistance-like connected except, been partial pressure ratio of each of the resistors changes the image forming apparatus according to any one of claims 18 to 22, characterized in Rukoto.   The control means turns on the first FET and turns off the second FET in the first mode that consumes predetermined power, and the first mode in the second mode that reduces the power consumption than the first mode. The third FET and the second FET are turned off, and the first FET and the second FET are turned on in the third mode in which the output current of the generation unit is larger than that in the first mode. Item 24. The image forming apparatus according to any one of Items 18 to 23.   The generation unit is a switching power supply having a transformer having a primary winding and a secondary winding, and a switching element for performing a switching operation for turning on or off a current flowing through the primary winding. Item 25. The image forming apparatus according to any one of Items 9 to 24.

Images